The long-term goals of this project are to develop an invertebrate, non- model system for the study of eye development. Because many processes of eye development are conserved across all animals, studying any animal can teach us about general processes of developmental systems, including those of humans. This study will characterize eye development in the crustacean Euphilodes morina. Males of this species have large compound eyes, while females have no compound eyes at all. Determining the developmental and genetic basis of this unusual eye dimorphism is a specific aim of the proposed study. This aim will be accomplished by isolating, specific aim of the proposed study. This aim will be accomplished by isolating, sequencing, and characterizing expression of four highly conserved eye-development genes in both crustacean males and females. Three hypotheses will be considered to explain the dimorphism: (1) Eye genes are sex-linked, (2) Differences in eye-gene expression are present between males and females (3) Eyes from early in female development but later are lost through programmed cell death (PCD). Each of the four genes to be considered has related genes involved in human eye development. Mutations in these genes are involved in many human diseases; not only of the eyes but also of the ears, nose, and kidneys. Determining how female E. morini manage to lack eyes without experimenting other developmental defects will provide new insight into the developmental genes of related human anomalies.